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Tyrosine hydroxylase - a marker for dopaminergic neurons in the central nervous system

Mon, 02/15/2016 - 15:48

Tyrosine hydroxylase is a member of the aromatic amino acid hydroxylase (AAAH) family. It is expressed throughout the central nervous system (CNS) and catalyzes the conversion of tyrosine to L-3,4-dihydroxyphenylalanine (L-DOPA), which can be, through a series of downstream enzymatic reactions, processed into the neurotransmitter and signaling molecule dopamine. Dopamine can then be further altered to produce norepinephrine or epinephrine. Tyrosine hydroxylase is the rate limiting enzyme in this pathway, also referred to as the catecholamine synthesis pathway.

Antibodies that detect tyrosine hydroxylase are often used to identify dopaminergic neurons in the CNS. In the mammalian retina, for instance, a subset of dopaminergic amacrine cells that form a single synaptic strata in the inner retina specifically express tyrosine hydroxylase and are often identified through tyrosine hydroxylase antibody staining (Wulle and Schnitzer, 1989). Multiple groups have used Novus tyrosine hydroxylase antibodies (#NB 300-110, #NB300-109) to mark this dopaminergic amacrine cell subpopulation (Contini et al., 2010; Fuerst et al., 2008; Zhang et al., 2012).

One group used a Novus anti-tyrosine hydroxylase antibody (#NB 300-110) to map cell-cell GABAergic synaptic connections that from between ON-bipolar cells and amacrine cells in the inner plexiform layer of the retina (Contini et al., 2010). This finding, in conjunction with previous studies, provides evidence for the hypothesis that in the mouse visual system dopaminergic amacrine cells exert inhibitory feedback in response to light by releasing both dopamine and GABA (Contini et al., 2010).

Another group used a Novus tyrosine hydroxylase antibody (#NB300-109) to assay the role of Down syndrome cell adhesion molecule (DSCAM) in retinal amacrine cell arborization and cell body spacing. This group used immunohistochemistry to visualize the morphology of tyrosine hydroxylase-expressing amacrine cells in DSCAM loss-of-function mutant mice. In the absence of functional DSCAM, dopaminergic amacrine cells are unable to from a properly structured arbor, and instead display hyperfasciculated processes and randomly dispersed cell bodies (Fuerst et al., 2008).